#pragma once
#include <algorithm>
#include <cstdint>
#include <cstring>

// Based on https://github.com/vog/sha1
/*
Original authors:
Steve Reid (Original C Code)
Bruce Guenter (Small changes to fit into bglibs)
Volker Grabsch (Translation to simpler C++ Code)
Eugene Hopkinson (Safety improvements)
Vincent Falco (beast adaptation)
*/
namespace cinatra {
namespace sha1 {

static std::size_t constexpr BLOCK_INTS = 16;
static std::size_t constexpr BLOCK_BYTES = 64;
static std::size_t constexpr DIGEST_BYTES = 20;

inline std::uint32_t rol(std::uint32_t value, std::size_t bits) {
  return (value << bits) | (value >> (32 - bits));
}

inline std::uint32_t blk(std::uint32_t block[BLOCK_INTS], std::size_t i) {
  return rol(block[(i + 13) & 15] ^ block[(i + 8) & 15] ^ block[(i + 2) & 15] ^
                 block[i],
             1);
}

inline void R0(std::uint32_t block[BLOCK_INTS], std::uint32_t v,
               std::uint32_t &w, std::uint32_t x, std::uint32_t y,
               std::uint32_t &z, std::size_t i) {
  z += ((w & (x ^ y)) ^ y) + block[i] + 0x5a827999 + rol(v, 5);
  w = rol(w, 30);
}

inline void R1(std::uint32_t block[BLOCK_INTS], std::uint32_t v,
               std::uint32_t &w, std::uint32_t x, std::uint32_t y,
               std::uint32_t &z, std::size_t i) {
  block[i] = blk(block, i);
  z += ((w & (x ^ y)) ^ y) + block[i] + 0x5a827999 + rol(v, 5);
  w = rol(w, 30);
}

inline void R2(std::uint32_t block[BLOCK_INTS], std::uint32_t v,
               std::uint32_t &w, std::uint32_t x, std::uint32_t y,
               std::uint32_t &z, std::size_t i) {
  block[i] = blk(block, i);
  z += (w ^ x ^ y) + block[i] + 0x6ed9eba1 + rol(v, 5);
  w = rol(w, 30);
}

inline void R3(std::uint32_t block[BLOCK_INTS], std::uint32_t v,
               std::uint32_t &w, std::uint32_t x, std::uint32_t y,
               std::uint32_t &z, std::size_t i) {
  block[i] = blk(block, i);
  z += (((w | x) & y) | (w & x)) + block[i] + 0x8f1bbcdc + rol(v, 5);
  w = rol(w, 30);
}

inline void R4(std::uint32_t block[BLOCK_INTS], std::uint32_t v,
               std::uint32_t &w, std::uint32_t x, std::uint32_t y,
               std::uint32_t &z, std::size_t i) {
  block[i] = blk(block, i);
  z += (w ^ x ^ y) + block[i] + 0xca62c1d6 + rol(v, 5);
  w = rol(w, 30);
}

inline void make_block(std::uint8_t const *p, std::uint32_t block[BLOCK_INTS]) {
  for (std::size_t i = 0; i < BLOCK_INTS; i++)
    block[i] = (static_cast<std::uint32_t>(p[4 * i + 3])) |
               (static_cast<std::uint32_t>(p[4 * i + 2])) << 8 |
               (static_cast<std::uint32_t>(p[4 * i + 1])) << 16 |
               (static_cast<std::uint32_t>(p[4 * i + 0])) << 24;
}

template <class = void>
void transform(std::uint32_t digest[], std::uint32_t block[BLOCK_INTS]) {
  std::uint32_t a = digest[0];
  std::uint32_t b = digest[1];
  std::uint32_t c = digest[2];
  std::uint32_t d = digest[3];
  std::uint32_t e = digest[4];

  R0(block, a, b, c, d, e, 0);
  R0(block, e, a, b, c, d, 1);
  R0(block, d, e, a, b, c, 2);
  R0(block, c, d, e, a, b, 3);
  R0(block, b, c, d, e, a, 4);
  R0(block, a, b, c, d, e, 5);
  R0(block, e, a, b, c, d, 6);
  R0(block, d, e, a, b, c, 7);
  R0(block, c, d, e, a, b, 8);
  R0(block, b, c, d, e, a, 9);
  R0(block, a, b, c, d, e, 10);
  R0(block, e, a, b, c, d, 11);
  R0(block, d, e, a, b, c, 12);
  R0(block, c, d, e, a, b, 13);
  R0(block, b, c, d, e, a, 14);
  R0(block, a, b, c, d, e, 15);
  R1(block, e, a, b, c, d, 0);
  R1(block, d, e, a, b, c, 1);
  R1(block, c, d, e, a, b, 2);
  R1(block, b, c, d, e, a, 3);
  R2(block, a, b, c, d, e, 4);
  R2(block, e, a, b, c, d, 5);
  R2(block, d, e, a, b, c, 6);
  R2(block, c, d, e, a, b, 7);
  R2(block, b, c, d, e, a, 8);
  R2(block, a, b, c, d, e, 9);
  R2(block, e, a, b, c, d, 10);
  R2(block, d, e, a, b, c, 11);
  R2(block, c, d, e, a, b, 12);
  R2(block, b, c, d, e, a, 13);
  R2(block, a, b, c, d, e, 14);
  R2(block, e, a, b, c, d, 15);
  R2(block, d, e, a, b, c, 0);
  R2(block, c, d, e, a, b, 1);
  R2(block, b, c, d, e, a, 2);
  R2(block, a, b, c, d, e, 3);
  R2(block, e, a, b, c, d, 4);
  R2(block, d, e, a, b, c, 5);
  R2(block, c, d, e, a, b, 6);
  R2(block, b, c, d, e, a, 7);
  R3(block, a, b, c, d, e, 8);
  R3(block, e, a, b, c, d, 9);
  R3(block, d, e, a, b, c, 10);
  R3(block, c, d, e, a, b, 11);
  R3(block, b, c, d, e, a, 12);
  R3(block, a, b, c, d, e, 13);
  R3(block, e, a, b, c, d, 14);
  R3(block, d, e, a, b, c, 15);
  R3(block, c, d, e, a, b, 0);
  R3(block, b, c, d, e, a, 1);
  R3(block, a, b, c, d, e, 2);
  R3(block, e, a, b, c, d, 3);
  R3(block, d, e, a, b, c, 4);
  R3(block, c, d, e, a, b, 5);
  R3(block, b, c, d, e, a, 6);
  R3(block, a, b, c, d, e, 7);
  R3(block, e, a, b, c, d, 8);
  R3(block, d, e, a, b, c, 9);
  R3(block, c, d, e, a, b, 10);
  R3(block, b, c, d, e, a, 11);
  R4(block, a, b, c, d, e, 12);
  R4(block, e, a, b, c, d, 13);
  R4(block, d, e, a, b, c, 14);
  R4(block, c, d, e, a, b, 15);
  R4(block, b, c, d, e, a, 0);
  R4(block, a, b, c, d, e, 1);
  R4(block, e, a, b, c, d, 2);
  R4(block, d, e, a, b, c, 3);
  R4(block, c, d, e, a, b, 4);
  R4(block, b, c, d, e, a, 5);
  R4(block, a, b, c, d, e, 6);
  R4(block, e, a, b, c, d, 7);
  R4(block, d, e, a, b, c, 8);
  R4(block, c, d, e, a, b, 9);
  R4(block, b, c, d, e, a, 10);
  R4(block, a, b, c, d, e, 11);
  R4(block, e, a, b, c, d, 12);
  R4(block, d, e, a, b, c, 13);
  R4(block, c, d, e, a, b, 14);
  R4(block, b, c, d, e, a, 15);

  digest[0] += a;
  digest[1] += b;
  digest[2] += c;
  digest[3] += d;
  digest[4] += e;
}

}  // namespace sha1

struct sha1_context {
  static unsigned int constexpr block_size = sha1::BLOCK_BYTES;
  static unsigned int constexpr digest_size = 20;

  std::size_t buflen;
  std::size_t blocks;
  std::uint32_t digest[5];
  std::uint8_t buf[block_size];
};

template <class = void>
inline void init(sha1_context &ctx) noexcept {
  ctx.buflen = 0;
  ctx.blocks = 0;
  ctx.digest[0] = 0x67452301;
  ctx.digest[1] = 0xefcdab89;
  ctx.digest[2] = 0x98badcfe;
  ctx.digest[3] = 0x10325476;
  ctx.digest[4] = 0xc3d2e1f0;
}

template <class = void>
inline void update(sha1_context &ctx, void const *message,
                   std::size_t size) noexcept {
  auto p = reinterpret_cast<std::uint8_t const *>(message);
  for (;;) {
    auto const n = (std::min)(size, sizeof(ctx.buf) - ctx.buflen);
    std::memcpy(ctx.buf + ctx.buflen, p, n);
    ctx.buflen += n;
    if (ctx.buflen != 64)
      return;
    p += n;
    size -= n;
    ctx.buflen = 0;
    std::uint32_t block[sha1::BLOCK_INTS];
    sha1::make_block(ctx.buf, block);
    sha1::transform(ctx.digest, block);
    ++ctx.blocks;
  }
}

template <class = void>
inline void finish(sha1_context &ctx, void *digest) noexcept {
  using sha1::BLOCK_BYTES;
  using sha1::BLOCK_INTS;

  std::uint64_t total_bits = (ctx.blocks * 64 + ctx.buflen) * 8;
  // pad
  ctx.buf[ctx.buflen++] = 0x80;
  auto const buflen = ctx.buflen;
  while (ctx.buflen < 64) ctx.buf[ctx.buflen++] = 0x00;
  std::uint32_t block[BLOCK_INTS];
  sha1::make_block(ctx.buf, block);
  if (buflen > BLOCK_BYTES - 8) {
    sha1::transform(ctx.digest, block);
    for (size_t i = 0; i < BLOCK_INTS - 2; i++) block[i] = 0;
  }

  /* Append total_bits, split this uint64_t into two uint32_t */
  block[BLOCK_INTS - 1] = total_bits & 0xffffffff;
  block[BLOCK_INTS - 2] = (total_bits >> 32);
  sha1::transform(ctx.digest, block);
  for (std::size_t i = 0; i < sha1::DIGEST_BYTES / 4; i++) {
    std::uint8_t *d = reinterpret_cast<std::uint8_t *>(digest) + 4 * i;
    d[3] = ctx.digest[i] & 0xff;
    d[2] = (ctx.digest[i] >> 8) & 0xff;
    d[1] = (ctx.digest[i] >> 16) & 0xff;
    d[0] = (ctx.digest[i] >> 24) & 0xff;
  }
}
}  // namespace cinatra
